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Tamron SP AF 17-50mm f/2.8 Di II LD Aspherical (IF) for Nikon

07/19/2006 11:58:28 AM · #1

//www.dpchallenge.com/challenge_history.php

I think most of the column headings are self-explanatory, but I really don't get "midrange score." If "average" means "arithmetic mean," meaning add up the total score (not avg. scores for each entry, but all the individual votes) across all entries and divide by the total number of votes, then I'd expect "midrange" to be the arithmetic median, meaning 50th percentile.

But at least in the single case I checked, it wasn't.

Canon EF 17-40mm f/4.0L USM

07/19/2006 12:25:09 PM · #2

You're right, something is buggered with that column. The stats are all lower than the median value, and I can't figure out what "midrange" should represent other than median (which is what it really should be labeled, IMO).
Also, I noticed that the low score is incorrect for the "Progress" challenge.
I'll bring these issues/questions up to the admins. Thanks for the heads up!

dahkota

Canon EOS-7D

07/19/2006 12:42:09 PM · #3

If you take the highest score of the challenge and the lowest score of the challenge, the midrange score is exactly 1/2 way between the two.

7.513-2.25= 5.263
5.263/2= 2.631
2.25+2.631= 4.881 (close enough, yes?)

I show 2.25 as the low score. Isn't that correct?

Tamron SP AF 17-50mm f/2.8 Di II LD Aspherical (IF) for Nikon

07/19/2006 02:37:21 PM · #4

Oh, you're right, Dahkota.

Thanks for figuring that out!

But it's really a meaningless number, so Kirbic, please do ask them to change it to median.

07/19/2006 03:01:08 PM · #5

I opened an administrative ticket... the 2.25 low score is correct only if DQ'd images are included in the stats, which they should not be. I'm thinking that if an image gets DQ'd after voting ends, it gets rolled into the stats.
On the midrange score, that now makes perfect sense mathematically, but as levyj413 opined, it's a pretty meaningless stat. I'd personally agree that median would be a much more useful number. I'll discuss it with Langdon and see if he's amenable to changing that.

Tamron SP AF 17-50mm f/2.8 Di II LD Aspherical (IF) for Nikon

07/19/2006 03:04:24 PM · #6

Thanks.

The progress low scorer wasn't DQ'd, though. Rather, it's a picture of a piece of paper with the hue shifted to match the DQ bar. :)

It had a legit score of 2.25. Here's the thumb (yes, it's a real thumbnail, not a color bar!

07/19/2006 03:06:53 PM · #7

Haha, you're right, good ol' charliebaker going for the brown (again). That's good, I was thinking we had a bug in the calculations.

07/24/2006 07:27:13 PM · #8

L has just informed me that the midrange score listed under the challenge history is now calculated as the median score, rather than the average of the high and low scores.
For those not statistically inclined, the median is the score that half of the images exceeded and half of the images were below.